1. Field of the Invention
The present invention generally relates to a method and system for processing traffic data, and more specifically, to a method and system for adjusting traffic lights.
2. Description of Related Art
Traffic control means effectively guiding and scheduling traffic flow through traffic lights at road intersections, in order to temporally-spatially split traffic flow that is likely to conflict. Traditional traffic control methods mainly include timing control, multi-period control, inducted or semi-inducted control, green wave band control and static region control. Timing control is based on Webster's equation for vehicle delay via which an approximation of best cycle can be obtained. Multi-period control is actually segmented timing control. Usually citizens' travel illustrates obvious regularity; for example, rush hours of traffic flow often take place at 7:00 a.m.-8:00 a.m. in the morning, 11:00 a.m.-12:00 p.m. at noon and 5:30 p.m.-6:30 p.m. Therefore, it is possible to select an optimal timing scheme for each period and perform multi-period control.
Currently, one adaptive control system that has been put into large-scale application is SCOOT. This system detects traffic flow data in real time by vehicle detectors, optimizes signal timing parameters by using a traffic model, and performs control by using communication networks, signal controllers and other hardware devices. In addition to formulating a timing scheme, this model may provide other information, such as delay, stopping times and congestion data, so as to serve traffic management and planning. Typically the SCOOT system divides an entire controlled region into a number of independent sub-regions. Intersections within the same sub-region use one identical signal cycle. An objective of periodical optimization is to control the vehicle waiting time average in sub-regions within certain range. And in order to prevent the sudden change of signal parameters from exerting adverse effect on traffic flow, SCOOT uses a small increment approach during optimization and adjustment.
A drawback of the SCOOT system is that the SCOOT system divides a region in a static way. Statically dividing a region is usually designated according to initial experience of traffic experts and can hardly adapt to the rapid road change demand. Besides, an objective of signal periodical optimization in the SCOOT system is to reduce vehicle waiting time average in static regions, which focuses on overall control of the entire region. Moreover, the SCOOT system performs adjustment by a change with a small step and thus, it perhaps cannot respond in time to the traffic demand during each period.